Low-water sensitive hydraulic fluids containing borate esters and formals

ABSTRACT

This invention relates to a low water-sensitive hydraulic fluid composition which contains from about 20 to about 96 percent by weight of at least one borate ester as the base fluid and additionally, from about 2 to about 40 percent of a bis (glycol ether) formal. Such low water-sensitive hydraulic fluids are high boiling compositions which also have desirable properties at low temperatures, particularly viscosity, and thus are useful under a wide variety of climatic and operational conditions.

United States Patent 1 Sawyer et al.

[ 51 Jan. 16, 1973 [S4] LOW-WATER SENSITIVE HYDRAULIC FLUIDS CONTAINING BORATE ESTERS AND FORMALS [75] lnventors: Arthur W. Sawyer, l-lamden; David A. Csejka, Orange, both of Conn.

[73] Assignee: Olin Corporation [22] Filed: April 12, 1971 [2]] Appl. No.: 133,407

Related [1.8. Application Data [63] Continuation-impart of Ser. No. 7l7,996, April 1,

1968, Pat. No. 3,625,899, which is a continuation-inpart of Ser. No. 653,338, July 14, 1967, abandoned.

52 us. Cl ..2s2/7s, 252/496 51 Int. Cl. ..C09k 3/00,Cl0m 3/48 58 Field of Search ..252/73,75,78,49.6

[56] References Cited UNITED STATES PATENTS 3,625,899 l2/l97l Sawyeretal. ..252/75 Milnes et al. ..252/75 Kress ..252/73 X Primary Examiner-Leon D. Rosdol Assistant Examiner-D. Silverstein Attorney-Eugene Zagarella, Jr., Gordon D. Byrkit, Donald F. Clements, F. A. lskander and Thomas P. ODay [57] ABSTRACT 32 Claims, No Drawings LOW-WATER SENSITIVE HYDRAULIC FLUIDS CONTAINING BORATE ESTERS AND FORMALS This application is a continuation-in-part of copending application Ser. No. 717,996 filed Apr. 1, [9:68 and now U.S. Pat. No. 3,625,899 which in turn was a continuation-in-part of application Ser. No. 653,338 filed July 14, 1967 and now abandoned.

This invention relates to new and improved, low water-sensitive hydraulic pressure transmission fluids for use in fluid pressure operating devices such as hydraulic brake systems, hydraulic steering mechanisms, hydraulic transmissions, hydraulic jacks, hydraulic lifts, etc. More particularly, this invention relates to hydraulic fluids having a low sensitivity to water which employ as the base fluid one or more borate esters of glycol monoethers and additionally a bis (glycol ether) formal. The term base fluid as used throughout the specification and claims means the major active ingredient (not necessarily present in the major or largest proportion) of the hydraulic fluid, i.e., that ingredient which is most active in maintaining the desired properties of the hydraulic fluid especially in the face of aqueous contamination.

A great number of hydraulic fluid compositions have been suggested in the art. Commonly, the hydraulic pressure transmission fluids, such as brake fluids are made up of three principal units. The first is a base stock or lubricant for the system which may include heavy bodied fluids such as polyglycols, castor oil, mixtures of these materials, etc. Diluents, which are employed for the purpose of controlling the viscosity of the fluid as represented by glycol ethers, glycols, alcohols, etc., form the second basic unit. Finally, the third basic unit is represented by an additive or inhibitor package comprising small quantities of materials which are added to control or modify various chemical and physical properties of the fluid, e.g., to reduce oxidation, to improve wetting and flow and to maintain the pH of the hydraulic system above 7 in order to minimize corrosion. By varying the composition, particularly desired properties can generally be attained. However, hydraulic fluids have been subject to increasingly stringent requirements with regard to properties, particularly boiling point and viscosity-temperature relationship. This had made it extremely difficult to produce a desirable fluid since very often a change in composition which improves one or more of the properties will detrimentally affect some other property. Thus, it has been possible to obtain hydraulic fluids having high boiling points by using higher molecular weight organic compounds, such as the polyoxyalkylene glycol ethers, as the major component, however, the viscosity of these fluids is generally unsatisfactory, particularly at low temperatures. This problem is magnified when water gets into the hydraulic fluid since many of the properties are affected, some to a substantial extent.

Hydraulic fluids, as exemplified by the commercial motor vehicle brake fluids, are hygroscopic by nature and therefore, absorb moisture from ambient atmospheres with resulting degradation of their boiling point. This effect that water has on the boiling point of hydraulic fluids has been studied extensively and a great deal of public interest has been generated concerning the safety qualities of hydraulic fluids especially brake fluids as is pointed out, for example by C. F. Pickett in an article entitled Automotive Hydraulic Brake Fluids,published as part of the 51st Mid-Year Meeting Proceedings of the Chemical Specialties Manufacturing Association, lnc., N.Y. (1965). As indicated in the above-noted article, when small amounts of water, e.g., 3.5 percent by weight was added to various commercial brake fluids, some having initial boil- .ing points of 500 F., the resulting fluid compositions exhibited boiling points below 300 F. In contrast, the hydraulic fluid compositions of this invention generally maintain boiling points of greater than 300 F. and more often greater than 320 F. and 350 F. when preferred embodiments are used, after the addition of 3.5 percent water.

The importance of having a hydraulic fluid which has a low sensitivity to water and thus can maintain the boiling point at levels above those previously found in available commercial fluids is more readily understood when the following facts are considered. First of all, it is known that hydraulic brake fluid temperatures can reach rather high levels and often approach and even exceed the 300 F. level. This is substantiated by the results of field studies in I966 by the Society of Au tomotive Engineers (See SP-338, Automotive Brake Evaluation Under Customer Usage Conditions, pp. 1 and 2, (1968)) wherein it was shown that brake fluid temperatures approached 270 F. under typical driving conditions of vehicles which were loaded only to their manufacturers recommended limit. lt could reasonably be assumed from these results, that when abnormal conditions are encountered temperatures would exceed 270 F. and approach and even pass 300 F It is also known that so-called conventional type motor vehicles often accumulate small amounts of moisture in their hydraulic fluids during usage. This is substantiated by results disclosed in a meeting of the SAE Hydraulic Brake Systems Actuating Committee in 1966 (See minutes of meeting of Oct. 26-27, 1966) and further by the report of Charles 8. Jordan, Effect of Water on Hydraulic Brake Fluid, U.S. Army Coating and Chemical'Laboratory, May, 1966. These arti-. cles clearly show that amounts of water have been accumulated in hydraulic brake fluids under use conditions in varying proportions and have often reached levels of up to 3.5 percent and even have been as high as 5 percent by weight. The fact that hydraulic fluids do accumulate some water during usage is further supported by the SAE Standard J-l703, Motor Vehicle Brake Fluid, which requires certain water tolerance tests to be passed after the addition of 3.5 percent water and also, requires a corrosion test to be passed after the addition of 5 percent water to the brake fluid. From the above discussion, it can readily be understood that hydraulic fluids under certain conditions can approach temperatures of the magnitude of 300 F. and higher and furthermore such fluids can accumulate small amounts of moisture during usage. Thus, hydraulic fluids which have low dry boiling points and are sensitive to water to a large degree can encounter problems such as vapor lock which can result in the failure of a hydraulic brake system and consequently cause an accident. This clearly illustrates the advantage of the hydraulic fluids of this invention which possess a high degree of water tolerance and are able to maintain their boiling points at higher and safer levels.

The seriousness of the problem of water accumulation and its efiects on the hydraulic fluid system is further signified by the fact that the US. Department of Transportation presently is considering acceptance of standards for motor vehicle brake fluids which ,would for the first time include a minimum wet reflux boiling point (equivalent to approximately 3.5 percent by weight of water added). The proposed standards include one for a fluid having a minimum dry reflux boiling point of 401 F. and a minimum wet reflux boiling point of 284 F. and another for a fluid having a minimum dry reflux boiling'point of 446 F. and a minimum wet reflux boiling point of 320 F. The term dry reflux boiling point as used herein is defined as the boiling point of the hydraulic fluid as delivered to the consumer or distributors (i.e., fluid ready for use). Wet reflux boiling point is the boiling point of the hydraulic fluid after. a discrete amount of water has been added thereto.

The above considerations clearly point out the need for a hydraulic fluid which has a low sensitivity to water and thus is able to maintain certain properties and characteristics when amounts of water commonly encountered during use are present. Inv addition, a hydraulic fluid which will be used under various climatic and operational conditions must maintain adequate viscosity (fluidity) over the temperature range of anticipated operating conditions so as to assure proper functionality of the system.

There are various hydraulic fluids known in the art as shown for example in Introduction to Hydraulic Fluids by Roger B. Hatton, Reinhold Publishing Corp. (1962); US. Pat. No. 2,998,389 issued to Chester M. White on Aug. 29, 1961 and U.S. Pat. No. 3,377,288 issued to Arthur W. Sawyer on Apr. 9, 1968. Generally, these fluids do not have the low water sensitivity that is required to maintain their original properties after there is an accumulation of moisture and additionally such fluids generally do not have the ability to operate under a wide variation of conditions.

One of the basic objects of this invention is to provide hydraulic pressure transmission fluids for use in hydraulic systems which retain to a high degree their original properties when water is added, i.e., they have a low sensitivity to water.

Another object is to provide hydraulic pressure transmission fluids which are high boiling compositions and which maintain relatively high boiling points even when water is added to the initial fluid composition.

Another object of this invention is to provide hydraulic pressure transmission fluids having a high degree of lubricity while maintaining desired viscosities within a predetermined range under wide variations of temperature conditions, especially subfreezing temperatures.

The hydraulic fluids of this invention generally comprise from about 20 to about 96 percent by weight, based on the total hydraulic fluid weight, of at least one borate ester of a glycol monoether as the base fluid and from about 2 to about 40 percent by weight of a formal of the glycol ethers. Generally the remainder of the fluid is made up of diluent and one or more additives.

The hydraulic fluids of this invention are especially desirable because they have a low water-sensitivity and also have a desired viscosity-temperature relationship over. a wide. range of temperature conditions. These properties make such fluids particularly attractive because'they can satisfactorily perform at low winter temperatures where the viscosity requirements are stringent and also can be used in warm weather climates and under heavy duty conditions particularly because of their high boiling points and low sensitivity to water. Additionally, the hydraulic fluids of this invention are of low cost, are essentially odorless and colorless, possess a high degree of compatibility with other fluids and exhibit a very low rate of corrosivity.

Another feature of the hydraulic fluids of this invention is that they have a satisfactory rubber compatibility. The significance of rubber compatibility and the rubber swelling properties of the fluids cannot be overlooked since too little swelling will result in leakage of the fluid passed the rubber cup sealing means and passed the piston and hydraulic cylinders with corresponding loss of power. On the other hand, fluids which cause too much rubber swelling are not desirable since they destroy the structural properties of the rubber sealing cups and rubber cylinders which, in turn, results in malfunction or inopcrativcness of the unit.

The hydraulic fluids of this invention generally comprise four principal units: l base fluid, (2) formal, (3) diluent and (4) additives.

BASE FLUID The base fluid employed in the novel hydraulic fluids of this invention generally comprises at least one borate ester of a glycol monoether. More particularly, the hydraulic fluids of this invention will comprise from about 20 to about 96 percent by weight, based on the total hydraulic fluid weight, of at least one borate ester of a glycol monoether. Preferably, the amount of borate ester will vary from about 30 to about 92 percent and more preferably from about 54.5 to about 92 percent by weight based on the total hydraulic fluid weight. When using hydraulic fluids which can safely operate under somewhat lower temperature conditions, the range of borate ester used may vary from about 20m about 54.4 percent and preferably from about 30 to about 54.4 percent by weight, based on the total weight of the hydraulic fluid.

Although a wide variety of borate esters can be employed as the base fluid in the novel hydraulic fluids of this invention, an especially useful class of borate esters are the so-called tri-borate esters of glycol monoethers having the general formula:

wherein R is a lower alkyl radical containing from one to four carbon atoms preferably one to two, R is alkylene of from two to four carbon atoms, preferably two to three, and is an integer from 2 to 4 inclusive. The R and R groups may be either straight or branched chain structures. Borates of the above-mentioned type include, for example: [CH (OCH CH O] 3- 2 5( 2)3 la- 3 1( 2 2)4 13 B, cHswcm Hoz s-B. H.(0 H. CHVCH3)3O]3"'B,[CH3(OCH2CHCH3)4O]3 B,[C2H5 (Q 2 a)2 ]aB,,- z s( z s)a ]s BLQ A Hz CHQJ 13- s 1( 2 a CHzOll';

While any of the borate esters defined by formula (1) may be used, the following borate esters are particularly useful: [Cl-1:,(OCH CH O] B, [C 11 CH2CH2)2 ]a 2 s( 2 2)s la 1 2- H5( z Hz)4 ]aB, 3H1( 2 Hz)3 laB, [C4H9(OCH2CH2)2O]3B and [C H9(OCH2CHz) Ol -B.

Borates of the above-mentioned type can be conveniently prepared by reacting orthoboric acid and the glycol monoether while in the presence of a waterazeotrope forming solvent. Water formed in the esterification reaction is continuously removed as the azeotrope. At first, the temperature of the reaction mixture is maintained between about 0 C. and about 190 C. and desirably at the distillation temperature of the water-solvent azeotrope. After essentially complete removal of the water formed during esterification, the excess solvent is conveniently removed from the reaction mixture by distillation. The borate ester product, which is left in a residue, may then be recovered by distilling under reduced pressure or by extraction with a suitable solvent followed by evaporation of the solvent. For example, the compound .[C l-1 (OCH CH O] B can be prepared by reacting two moles of QHAOCFIQCITDQCH, 0.67 mole 5f orthobo ric acid and 700 ml. of ethylbenzene with heating and mixing to yield 198 grams of the ester, a water-white liquid boiling at 222-223 C. (5 mm. Hg). It is noted that in the preparation of these esters, a small proportion of concomitant reaction products may be formed and other minor impurities may also be present. Generally, the predominant portion of such otherreaction products formed will be a boroxine type compound having the following general structure:

wherein R is derived from the particular glycol ether being used, e.g., CH;,(OCH CH O, C H (OCH CH O-, etc."1" he amount of such concomitant reaction products formed and other impurities present may be up to about 10 percent by weight if the reacted mixture is not distilled. Distillation will reduce the amount of other reaction products and impurities to about 1 percent or less, however, either the distilled or undistilled product can be used provided the reaction medium or solvent is stripped off. Theterm borate ester" as used in the specification and claims is intended to include relatively pure borate ester as well as crude borate ester which contains impurities and other by-products formed during preparation as described above. The preparation of the tri-borate esters per se is more completely described in U. S. Pat. No. 3,080,412 issued to D. M. Young on Mar. 5, 1963. It is of interest to note that this patent (U.S. Pat. No. 3,080,412) discloses the use of tri-borate esters, such as tris [2(2- ethoxyethoxy)ethyl] borate, as stabilizers and corrosion inhibitors for lubricants and non-aqueous hydraulic fluids. However, use of these esters for such purposes, i.e., as a stabilizer or corrosion inhibitor, would not impart satisfactory low water sensitivity to the hydraulic fluid since such usage would generally be in very small or minor proportions (e.g., from. 0.5 to 2 percent) in accordance with the generally accepted practice in the art (e.g., see U.S. Pat. No. 3,403,104 issued to P. B. Sullivan on Sept. 24, 1968). Additionally fluids containing such amounts of esters would not have desired temperature-viscosity relationship over the wide range of operating conditions as provided by the hydraulic fluids of this invention.

A second highly useful class of borate esters includes compounds of the general formula: [R,(OCH CHR m' 2 3)n ]3' (1 wherein R and R are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20 and R is alkyl of from one to four carbon atoms and with proviso that one of R and R is methyl and one of R and R is hydrogen. R may be a straight chain or branched alkyl. Borate esters of Type 11 can be prepared in the general way as those esters previously described (Type 1) above, utilizing the so-called block type glycol monoethers. The preparation of esters of Type 11 is described in detail in US. Pat. No. 3,316,287 issued to L. G. Nunn, Jr. et al. on Apr. 25, 1967.

Type II borate esters useful in preparing the novel fluids of this invention include, for example:

Another class of borate esters useful in the fluid compositions of this invention include esters having heteric oxyalkylene chains, that is, oxyalkylene chains in which oxyethylene and oxypropylene units are distributed randomly throughout the chain. These Type 111 esters have the general formula:

Rg represents a heteric oxyalkylene chain having the formula:

(lll) where the sum of r and s is not more than 20 and wherein the weight percent of oxyethylene units in the said chain is not less than 20 based on the total weight of all the oxyalkylene units in the chain and R is alkyl of from one to four carbon atoms and may be straight or branched chain. The preparation of Type III esters can be accomplished in the same general manner as the preparation of Types 1 and 11 described above by reacting orthobon'c acid in the presence of toluene with a heteric glycol monoether of the formula:

3 ,7 l l ,4 1 2 7 8 R,[Rg]OH 6T1tB'SYprefeiaEIYfm 3.' The mama R groups may be straight or branched chained and it is also intended where R, and Rg have the same meaning as previously that the alkylene oxide group (RG) in the above set forth. Glycol monoethers of this class can be conmula (v) include mixtures ofsaid alkylene oxides. veniemly prepared by methods know" in the an Illustrative of the above type formals (V) are the folsuch as the process described in US. Pat. No. lowing compounds: 2,425,845 issued to W. J. Toussaint et al. on Aug. 19, fcgmwmm; H. H a 4 )z]z z 7 A fourth type of borate ester suitable for use in the [CH,O(C,l-l 0);,],CH

fluid compositions of this invention have the general 2 s 2 4 )2]2 2 formula: 4 9 2 4 )lz 2 O(RsCHCHzO) --(RCHCH2O)".T3

wherein T and T are each an independently [C.,l l O(C I-l O) CH selected alkyl group having from one to four carbon [CH3O(CH2CHCH O)] CH atoms, R R R R R and R, are independently s 2 3 )z]2 2 selected from the group consisting of hydrogen and 2 s 2 3 )2]2 e methyl, n and m are positive integers independently a z 4 z 3 )lz z While any of the above formals defined by formula selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than (v) may be P the followmg bmglycol ether) n als are particularly useful:

two of the chains is the sum of n and m the same. It is -....A- also noted that T1, T2, and T may be a straight or ggg gg gg l g fi branched chain alkyl group. s 2 4 2 z z Borate esters of this type can be prepared in the same [C H ,,()((j CH way as the process described for Type I esters previ- [C H O(C l-l.,O)] CH ously mentioned. 4 9 2 4 )3]2 2 Type IV borate esters suitable for use in the fluids of The above formals may be prepared by reacting the this invention include, for example: appropriate glycol with paraformaldehyde and remov- 0(omcnomm-wmomoncm 0wmomm-wmoncmmom I It is further noted that borate esters of Types ll, Ill ingthe water bfcondensation whichforms. Preparative and [V will include concomitant reaction products and techniques are commonly known in the art, e.g., British other impurities of the type as described above for Pat- NO- 506,613 June 1, 1939); Chemical Abstracts, Type I esters. Reference to these types of borate esters 9325 discloses a P CeSS for the preparation in the specification and claims is intended to include of condensation Products of aldehydes with P y y relatively pure borate ester as well as crude borate ester alcohols of P l ethel's thereof: other known which contains impurities and other byproducts methods of preparation are disclosed in Canadian Pat.

formed during preparation as described above for Type 390,733 (Aug- 1940); Chemical Abstracts, 34,

L 6948 (1940), and in J.Am.Chem.Soc., Formaldehyde bis(B-ethoxyethyl) and bis(B-ethox ethox eth l) FORMAL COMPONENT acetal," by M. Sulzbacher, 72, 2795-6, 1150 y y The formal portion of the hydraulic, fluid composi- While the hydraulic fluid composition of this invention of this invention will generally comprise from tion may contain from about 2 to about 40 percent by about 2 to about 40 percent by weight, based on the weight, based on the total weight of the hydraulic fluid, total weight of the hydraulic fluid, of one or more of the above formals (V), preferred embodiments inbis(glycol ether) formals having the formula: clude about 2 to about 15 and more preferably from about 2 to about 10 percent by weight.

[R,,O(R ,O),],Cl-l v The use of these formals enable the hydraulic fluids of this invention to function over a wide range of cliwherein R is alkyl of one to six carbon atoms, matic and operational conditions particularly because preferably one to four, R, is alkylene of two to four carof desirable temperature-viscosity relationships which bon atoms, preferably two to three and x is an integer such hydraulic fluids possess.

(a) glycol monoethers or diethers (b) glycols and polyglycols and (c) aliphatic saturated alcohols.

More particularly, the glycol monoethers or diethers have the formula:

R[O-R"],,OR' (VI) wherein R is alkyl of from one to four carbon atoms, preferably one to two, R is hydrogen or alkyl of from one to four carbon atoms, preferably one to two, R is alkylene of two to four carbon atoms, preferably two to three, and y is 2 to 4. The R, R' and R" groups may be straight chained or branched and it is also intended that the alkylene oxide groups (OR") in the above formula (VI) include mixtures of said alkylene oxides.

Illustrative of the diluents of this type (VI) are the following compounds: diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol mono-n-butyl ether, tetrapropylene glycol monomethyl ether,

tetrapropylene glycol monoethyl ether, dibutylene glycol monomethyl ether, dibutylene glycol monoethyl ether, tributylene glycol monomethyl ether, tributylene glycol monoethyl ether, tributylene glycol mono-npropyl ether, tetrabutylene glycol monomethyl ether, tetrabutylene glycol monoethyl ether, tetrabutylene glycol mono-n-butyl ether and the corresponding diethers thereof. It is further noted that the above diluents include the various isomers of the respective compounds and mixtures thereof.

While any of the above glycol ethers defined by formula (VI) may be used, the following glycol ethers are particularly useful: diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and tetraethylene glycol monobutyl ether.

The glycol ethers are the most preferred diluent since their use will result in a fluid having a desirably high boiling point with good viscosity and water solubility properties. Most preferred of the glycol ethers are the ethylene glycols.

The second group of useful diluents are the glycols and polyglycols, including alkylene, polyalkylene and polyoxyalkylene glycols, having a molecular weight of from about 60 to about 450 and preferably from about 100 to about 300. Illustrative of such type diluents are the following compounds: ethylene glycol, propylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, polyethylene glycol and polypropylene glycol.

The use of the glycols and polyglycols as diluents is not a s desirable as the glycol ethers since their use may result in some loss of fluidity at very low temperatures,

. however, they may be used in conditions where the requirements are not as demanding.

The third type of useful diluents are aliphatic, saturated monohydric alcohols containing from six to 13 carbon atoms, preferably from eight to 10. Illustrative of such diluents are the following alcohols: hexanol, octanol, isooctanol, decanol, isodecanol, dodecanol, and tridecanol.

Since the use of the aliphatic alcohols in a high boil ing hydraulic fluid may result in some loss of water solubility, they are not as desirable as the glycol ethers. However, they may be used in conditions where the requirements are not as stringent.

The diluent portion of the hydraulic fluids of this invention generally will comprise from 0 to about 78 percent by weight, preferably from about 2 to about 70 and more preferably from about 6 to about 45 percent by weight, based on the total weight of the hydraulic fluid composition.

While the above diluents, especially the glycol ethers, are particularly preferred, other diluents may be used if the desired properties and characteristics of the hydraulic fluid can be attained. For example, certain diesters derived from organic aliphatic acids and aliphatic alcohols might be usefully employed. Examples of diesters which might be used include dibutyl adipate, bis(methoxyethyl azelate, diisopropyl succinate, dipropylene glycol diproprionate and triethylene glycol dibutyrate.

ADDITIVES When desired, various additives may be added to the hydraulic fluids of this invention to control or modify various chemical and physical properties of the fluids. Among the various types of additives which can be added to the hydraulic fluids of this invention are included: inhibitors for pH and corrosion control, antioxidants, rust inhibitors, viscosity index improvers, pour point depressants, lubricating additives, antifoamants, stabilizers, demulsifiers, dyes and odor suppressants. Generally, the total amount of additives which may be incorporated into the fluid composition will vary depending on the particular composition and the desired properties. More particularly, the total amount of additives will comprise from 0 to about 10 percent and preferably from about 0.1 to about 8.0 percent by weight based on the total weight of the hydraulic fluid composition.

For example, inhibitors for pH and corrosion control, such as alkaline inhibitors as exemplified by the alkali metal borates, can be employed in an amount sufficient to maintain alkaline conditions in the fluid compositions, e.g., a pH value of from about 7.0 to about 1 1.5. These inhibitors are generally added in an amount of from 0 to about 8.0 percent by weight based on the total weight of the hydraulic fluid composition and preferably from about 0.2 to about 6.0 percent by weight on the same basis. Useful inhibitors include alkali metal borates, such as sodium borate, potassium tetraborate, etc.; sodium meta arsenite; alkali metal salts of fatty acids, such as potassium oleate, the potassium soap 'of rosin or tall oil; alkylene glycol condensates with alkali metal borates, such as the ethylene .,dKlre by hsrl!mar ne d -Nwst amin n y amine, diamylamine, dioctylamine, salicylal monoethanolamine, dimB-naphthyl-p-phenylene diamine, N ,N '-disa1icy1idene-l ,2-propanediamine,

N,N"-disa1icylal ethylene diamine, dicyclohexylamine, and amine salts such as mono or dibutyl ammonium borate; phosphites, such as triphenyl phosphite, tri(tertamylphenyl) phosphite, diisopropyl phosphite, etc.; mercaptobenzotriazole; morpholine compounds including alkyl morpholines having from one to four carbon atoms in. the alkyl group such as N-ethyl morpholine, N-isopropyl morpholine, N-butyl morpholine; N-phenyl morpholine, N-(2-aminoethy1) morpholine, N-(2-hydroxyethyl) morpholine, etc.; phosphates, including the alkali metal phosphates, dibutyl amine phosphates, the dialkyl acid phosphates and amine salts thereof; triazoles including benzotriazole, l ,Z-naphthotriazole, 4- nitrobenzotriazole, tolutriazole, aminobenzotriazoles such as 5-acylaminobenzotriazole, and alkyl triazoles having one to carbon atoms in the alkyl group as exemplified by methyl triazole, ethyl triazole, n-propyl triazole, tertiary butyl triazole, hexyl triazole, isodecyl triazole, etc. Other useful corrosion inhibitors include adenine, 4-methy1imidazole, 3,5-dimethy1 pyrazole, 6- nitroidazole, imidazole, benzimidazole, quanine, in-

dazole,v ammonium. dinonylnaphthaline sulfonate, dioleyl thiodipropionate, ethylbenzoate, ethyl-paminobenzoate, cyclohexyl ammonium nitrite,

diisopropyl ammonium nitrite, butynediol, glycerin, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert. butyl-4-hydroxybenzoyl), 4,4-methylene bis(2,6-di-tert. butylphenyl), 4-hydroxymethyl-2,6-di-tert. butylphenyl, 4,4- methylene bis(4-methyl-6-tert. butylphenyl), salicylalo-aminophenol, 2,6-di-tert. butyI-Z-dimethylamino-pcresol, 4,4'-thio bis( 6-tert. butyl-o-cresol), Mixtures of the above-mentioned inhibitors can be employed if desired.

While any of the above-mentioned inhibitors may be used for pH and-corrosion control, the following inhibitors are particularly useful: glycerin, butynediol,

diethanolamine, methyl diethanolamine, mixed isopropanolamines, diisopropanolamine and triisopropanolamine.

An antioxidant may be used as an additive in the hydraulic fluid compositions of this invention ifydiphenylamine, etc.; hindered phenols such as dibutyl 856.561, 2,6 dimethyl-p-cresol, butyl ated 2,2-di-(4- hydroxyphenyl) propane, n-butylated aminophenol, butylated hydroxyanisoles, such as 2,6-dibuty1-phydroxyanisole; anthraquinone, dihydroxyanthraquinone, hydroquinone, 2,S-di-tertiarybutylhydroquinone, Z-tertiary butylhydroquinone, quinoline, p-hydroxydiphenylamine, phenyl benzoate, 2,6-dimethy1 pcresol, p-hydroxyanisole, nordihydroquaiaretic acid, pyrocatechol, styrenated phenol, polyalkyl polyphenols, sodium nitrite, etc. Mixtures of the abovementioned antioxidants can be employed, if desired. It should be emphasized that with a variety of the fluids of this invention, which are suitable for a wide range of in dustrial application, a separate antioxidant is not required.

While any of the above-mentioned antioxidants may be used, the following antioxidants are particularly preferred: sodium nitrite and dioctyl diphenylamine.

The above-noted inhibitors and additives are merely exemplary and are not intended as an exclusive listing of the many well-known materials which can be added to fluid compositions to obtain various desired properties. Numerous additives useful in hydraulic fluids are disclosed in Introduction to Hydraulic Fluids by Roger E. Hatton, Reinhold Publishing Corp., (1962).

Formulation of the novel hydraulic fluids of this invention is accomplished by blending the components to I a homogeneous stage in a mixing vessel. The preferable blending temperature is from about 50125 F. It is preferable to warm the solution during preparation to facilitate dissolution. The blending of the compounds is conveniently conducted at atmospheric pressure in the absence of moisture.

in general, any suitable method can be used in preparing the liquid compositions of this invention. The components can be added together or one at a time, in any desired sequence. It is preferable, however, to add the antioxidant and alkaline inhibitor as a solution in the glycol ether component. All components are mixed until a single phase composition is obtained.

The following examples which illustrate various embodiments of this invention are to be considered not limitative.

EXAMPLE 1 A hydraulic fluid was prepared having the following composition:

This fluid composition was tested according to the procedures set forth in Society of Automotive Engineers Standard .11703. The data relating to these tests, which illustrate the outstanding properties of this fluid is shown in Table 1.

The reflux boiling point (dry) of the above fluid was 4 measured and found to be 532 F. at atmospheric pressure. To test the water insensitivity of the fluid com- TABLE 1.PROPERTIES 0F HYDRAULIC FLUID 01" EXAMPLE 1 (Tests conducted according to procedures set forth in Society of Auto motive Engineers Standard J 1703 Specification Test Test SAE .11703 results Boiling point 374 F., min 532 F. Flash point 170.6 F., min 325 F. Viscosity:

40 F 1,800 0.5., max 1,667 cs. 122 F m 6.7 cs. 212 F 05., min. 6.25 cs. pH value 7.011.5 7.0. Fluid stability:

Heat stability (boiling point change) 5.4 FA 4 F. Chemical stability 3.6 F. max 0. Corrosion test (max. wt. chg. in mg./sq.

Cooper. Brass Cast iron Aluminum allo Steel Tin. Pitted or roughened metal strips. Jelling fluid water mixture .do. Crystalline deposit jar walls or do Do.

strips. Sedimentation, percent by volume 0.1 max 0.05 pH value 7.011.5 7.6. Rubber cups:

Swelling SoItening .l. Disintegra ion.

Fluidity and appearance: 40 F., six days:

Black contrast lines HP chart- Clearly discernible Clear. Stratification-sedimentation. None None. Air bubble travel time 10 sec. max 2% sec. 58 F., six hours:

Black contrast lines HP chart Clearly discernible Clear. Strotification-sedimcntation None None. Air bubble travel time 35 sec. max 3 sec. Evaporation:

Percent loss 80 max 58.5. Gritty or abrasive residue. None. lour point F. Water Tolerance:

40 F., .14 hours:

Black contrast. lines 111 chart. Clearly dlscernible Clear. Sttntification-sedimentation None None. Air bubble travel time 10 sec. max 3 sec. 140 F., 24 hours:

Stratification None Clear. Sedimentation, percent by 0.05 (0.15) max. 0.05.

volume. Compatibility:

40 F., 24 hours:

Black contrast lines HP chart. Clearly dlscernible Clear. Stratification-sedimentation None None. 140 F., 24 hours:

Stratification do None. Sedimentation, percent by vol- 0.05 max 0.05.

ume. Resistance to oxidation:

Fitting of metal strips:

luminum None None. Cast iron do Do. Gum deposit:

Aluminum Trace 1)o. Cast iron do Do. Wt. chg. in mg./sq. cm.:

Aluminum 0.05 0.00. Cast iron 0.30 000. Effect on Rubber (SB It):

Swelling 0.0060.055 0.031

..... 10 points max. 3.

. gr Specific gravity, 00/60 F Pounds per gallon, 00 F tolor. Gardner Plus 0.05 degree for each degree that the boiling point exceeds 437 F. 1 Commercial packaged fluid.

EXAMPLE 2 A hydraulic fluid was prepared having the following composition:

EXAMPLE 3 A hydraulic fluid was prepared having the following composition:

Percent by Weight Borate Ester [C2H5(0C2H)30]3-B 51.80 [C H (OC H O] -B 18.20 Triethylene glycol monoethyl ether 19.35 i a 2 A )l-2CH2 Mixed isopropanolamines (10-15% mono, 40-50% di, 40-50% tri) 3.00 Glycerin 2.00 Butynediol 0.50 Dioetyl diphenylamine (Van Lube 81 produced by R. T. Vanderbilt Co.) 0.10 Sodium nitrite 0.05

100.00 Properties: Reflux boiling point (dry) 481 F. Reflux boiling point (wet) (3.5 ml. water m1. fluid) 339 F. Viscosity at 40 F. 1,515 cs.

EXAMPLE 4 A' hydraulic fluid was prepared having the following composition:

Percent by Weight Borate Ester lC,H (OC,H.),0] -B 51.80 [C,H.-,(OC H.),O] -B 18.20 Triethylene glycol monoethyl ether 4.35 [CH,0(C H O)],CH 20.00 Mixed isopropanolamines (l0l 5% mono, 40-50% di, 40-60% tri) 3.00 Glycerin 2.00 Butynediol 0.50 Dioctyl diphenylamine (Van Lube 81 produced by R. T. Vanderbilt Co.) 0.10 Sodium nitrite 0.05

100.00 Properties:

Reflux boiling point (dry) 453F. Reflux boiling ,point (we t) (3.5 ml. water 100 ml. fluid) 333F. Viscosity at -40F. 720 cs.

EXAMPLE 5 A hydraulic fluid was prepared having the following composition: l 0

Percent by Weight Borate Ester 2 s( z 4)a 1: 51.80 [C2H5(0C2H4 )4 1:1 18.20 Triethylene glycol monoethyl ether 19.35 [CH O(C H,O),,CH, 5.00 Mixed isopropanolamines (IO-15% mono, 40-50% di, 40-50% tri) 3.00 Glycerin 2.00 Butynediol 0.50 Dioctyl diphenylamine (Van Lube 81 roduced by R. T. Vanderbi t Co.) 0.10 Sodium nitrite 0.05

100.00 Properties: Reflux boiling point (dry) 505F. Reflux boiling point (wet) (3.5 ml. water 100 ml. fluid) 345 F. Viscosity at 40 F. 1,865 cs.

EXAMPLE 6 A hydraulic fluid was prepared having the following composition:

Percent by Weight Borate Ester 1 2 5( 2 )a 1a 5 l .80 1 2 s( z 4)4 1s- 18.20 40 Triethylene glycol monoethyl ether 4.35 1 4 )22 20.00 Mixed isopropanolamines (IO-15% mono, 40-50% di, 40-50% tri) 3.00 Glycerin 2.00 Butynediol 0.50 Dioctyl diphenylamine 4 5 (Van Lube 81 produced by R. T. Vanderbilt Co.) 0.10 Sodium nitrite 0.05

100.00 Properties: Reflux boiling point (dry) 523 F. Reflux boiling point (wet) (3.5 ml. water 100 ml. fluid) 354 F. Viscosity at 40 F. 1,415 cs.

EXAMPLE 7 A hydraulic fluid was prepared having the following composition:

Percent by Weight Borate Ester 1 5( 4 )3 13- 51.80 [C,H (0C,H,) O],-B 18.20 Triethylene glycol monoethyl ether 19.35 5 5 [C H,O(C,H O)],CH, 5.00 Mixed isopropanolamines 10-15% mono, 40-50% di, 40-50% tri) 3.00 Glycerin 2.00

Butynediol 0.50 Dioctyl diphenylamine (Van Lube 81 roduced by R. T. Vanderbi t Co.) 0.10 Sodium nitrite 0.05

100.00 Properties: Reflux boiling point (dry) 502 F. Reflux boiling point (wet) (3.5 ml. water m1. fluid) 343 F. Viscosity at 40 F. 1,771 cs.

EXAMPLE 8 A hydraulic fluid was prepared having the following composition:

Percent by Weight Borate Ester z s( 2 )a 1s 51.80 2 2 4) ]r-B 18.20 Triethylene glycol monoethyl ether 19.35 [C11,0(C,H.O CH, 5.00 Mixed isopropanolamines (10-15% mono, 40-50% di, 40-50% tri) 3.00 Glycerin 2.00 Butynediol 0.50 Dioctyl diphenylamine (Van Lube 81 produced by R. T. Vanderbilt Co.) 0.10 Sodium nitrate 0.05

100.00 Properties: Reflux boiling point (dry) 504 F. Reflux boiling point (wet) (3.5 ml. water +100 m1. fluid) 343 F. Viscosity at --40 F. 2,083 cs.

EXAMPLE 9 A hydraulic fluid was prepared having the following composition:

Percent by Weight 1 s( 2 4):| 1r- 20.00 Triethylene glycol monomethyl ether 58.00 1 2 s 2 4 ):1: 2 15.00 Polyethylene glycol (M.W. 300) 5.00 Diethanolamine 2.00

100.00 Pro erties: Re ux boiling point (dry) 490 F. Reflux boiling point (wet) (3.5 ml. water+ 100 ml. fluid) 308 F. Viscosity at 40 F. 522.3 cs.

EXAMPLE 10 A hydraulic fluid was prepared having the following composition:

Percent by Weight 1 n( z 4)a 1s-' 25.00 Tetraethylene glycol monoethyl ether 15.00 Triethylene lycol monoethyl ether 39.00 1 4 o z 40)J12CH2 20-00 Monoethanolamine 1.00

Properties:

Reflux boiling point (dry) 436 F. Reflux boiling point (wet) (3.5 ml. water+ 100 ml. fluid) 304 F. Viscosity at 40 F. 607.1 cs.

EXAMPLE 1 l A hydraulic fluid was prepared having the following composition:

.10 Percent by Weight [CH;,(OC,H );,(OCH CHCH,) (OC,H )O],,-B 30.00 Triethylene glycol monomethyl ether 57.00 1 [CH,O(C,H,O),,CH, 10.00 Triisopropanolamine 3.00

100.00 Properties: Reflux boiling point (dry) 504 F. Reflux boiling point (wet) (3.5 ml. water 100 ml. fluid) 308 F. Viscosity at -40 F. 516.3 cs.

EXAMPLE '1 2 A hydraulic fluid was prepared having'the following composition:

Percent-by 3O Weight [C,H,,0(50% c,u,o+ 50% cn cncu op n 35.00 (Prepared using Union Carbide glycols Veon SO-HBSS) Triethylene glycol monoethyl ether 22.00 Polyethylene glycol (M.W. 300) 10.00 [CH O(C H,O) CH 30.00 Diisopropanolamine 2.5 Dioctyl diphenylamine (Van Lube 81 produced by 40 R. T. Vanderbilt Co.) 0.5

100.00 Properties: Reflux boiling point (dry) 542 F. Reflux boiling point (wet) (3.5 ml. water 100 ml. fluid) 315 F. Viscosity at 40 F. 848.8 cs.

EXAMPLE 13 so A hydraulic fluid was prepared having the following composition:

Percent by weight 5 5 Borate Ester [CH;,(OC,H,),O],B 30.0 Tetraethylene glycol monomethyl ether 22.0 Triethylene glycol monoethyl ether 42.0 i motcato) 12cm 5.0 Monoethanolamine 1.0

100.00 Properties: Reflux boiling point (dry) 467 F. Reflux boiling point (wet) 321 F. (3.5 ml. water ml. fluid) Viscosity at -40" F. 660 cs EXAMPLE 14 A hydraulic fluid was prepared having the following composition:

Percent by Weight Borate Ester s( 4)=' l=- 2 B( 2 4)2 l3 Triethylene glycol monomethyl ether 20.0 Triethylene glycolmonobutyl ether 17.0 Polyethylene glycol (M.W. 300) 15.0 2 a C:H4O)2']:CH2 Monoisopropanolamine 3.0

Properties Reflux boiling point (dry) 445 F. Reflux boiling point (wet) 321 F. (3.5 ml. water+ 100 ml. fluid) Viscosity at 40 F. 2,437 cs EXAMPLE 15 A hydraulic fluid was prepared having the following composition:

What is claimed is:

l. A hydraulic fluid composition consisting essentially of (A) from about 20 to about 96 percent by weight, based on the total weight of the hydraulic fluid composition, of at least one base fluid or lubricant selected from the group consisting of (a) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, R,, is alkylene of from two to four carbon atoms and y is an integer of from 2 to 4; (b).a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, R and R are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with the proviso that one of R and R is methyl and one of R and R is hydrogen; (c) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, R, is a heteric oxyalkylene chain of the formula:

wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula:

wherein T and T are each an independently selected alkyl group having from one to four carbon atoms, R R R R R and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same;(B) from about 2 to about 40 percent by weight, based on the total weight of the hydraulic fluid composition, of at least one bis( glycol ether) formal having the formula:

wherein R,, is alkyl of one to six carbon atoms, R, is alkylene of two to four carbon atoms and x is an integer of 1 to 5 and (C) from 0 to about 78 percent by weight, based on the total weight of the fluid composition, of at least one diluent selected from the group consisting of: (aa) glycol ethers having the formula:

wherein R is alkyl of from one to four carbon atoms, R is selected from the group consisting of hydrogen and alkyl of from one to four carbon atoms, R is alkylene of from two to four carbon atoms and y is an integer of from 2 to 4; (bb) glycols and polyglycols having a molecular weight of from about 60 to about 450 and (cc) aliphatic saturated monohydric alcohols having from six to 13 carbon atoms.

2. The hydraulic fluid composition of claim 1 4 wherein said formal has an alkyl R, group of one to four carbon atoms, an alkylene R group of two to three carbon atoms and x is l to 3.

3. The hydraulic fluid composition of claim 2 wherein from about 2 to about percent by weight, based on the total weight of the hydraulic fluid, of said formal is present.-

4. The hydraulic fluid composition of claim 3 wherein said formal is selected from the group consisting OfI a 2 4 )]2 2, 3 2 4 )alz 2 2 n.r 2 4 )2]2 2 4 Q 2 4 )]2 2 and l t u z r hlz z- 5. The hydraulic fluid composition of claim 2 wherein said base fluid or lubricant is a borate ester of type (a).

6. The hydraulic fluid composition of claim 5 wherein said base fluid or lubricant consists essentially of from about to about 54.4 percent by weight, based on the total weight of the hydraulic fluid composition.

7. The hydraulic fluid composition of claim 5 wherein said base fluid or lubricant consists essentially of from about 54.5 to about 92 percent by weight, based on the total weight of the hydraulic fluid composition.

8. The hydraulic fluid composition of claim 7 wherein said borate ester of type (a) has an alkyl R group of one to two carbon atoms and an R alkylene group of two to three carbon atoms.

9. The hydraulic fluid composition of claim 7 wherein said base fluid or lubricant is "a borate ester selected from the group consisting of: [CH (OCH HZ)5 3L-B, 2H5(OCHCH2 )20]B, 2115 HzCH2)2 ]aB, 2H5( H2-CH2)4 ]aB, a-

[ 4H9( 2 H2)2 ]3B 10. The hydraulic fluid composition of claim 9 wherein from about 2 to about 15 percent by weight, based on the total weight of the hydraulic fluid composition, of said formal is used.

11. The hydraulic fluid composition of claim 10 wherein said formal is selected from the group consisting of: 3 2 4 )]2 2, s 2 4 )2]2 2 a z 4 )3]z z, z 5 z 4 )2l2 z, 4 9 2 4 )]z 2 and 4 Q 2 4 )alz z 12. The hydraulic fluid composition of claim 11 wherein said diluent is present in amounts of from about 2 to about percent by weight, based on the total weight of the hydraulic fluid composition.

13. The hydraulic fluid composition of claim 12 wherein said diluent is selected from the group consisting of diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and tetraethylene glycol monobutyl ether.

14. The hydraulic fluid composition of claim 13 wherein from about 0.2 to about 6.0 percent by weight of an inhibitor for pH and corrosion control is used.

15. The hydraulic fluid composition of claim 14 wherein said inhibitor is selected from the group consisting of glycerin, butynediol, diethanolamine, methyl diethanolamine, mixed isopropanolamines, diisopropanolamine and triisopropanolamine.

16. The hydraulic'fluid composition of claim 15 wherein from about 0.001 to about 1.0 percent by weight, based on the total weight of the hydraulic fluid composition, of an antioxidant is used.

17. The hydraulic fluid composition of claim 16 wherein said antioxidant is selected from the group consisting of sodium nitrite and dioctyl diphenylamine.

18. The hydraulic fluid composition of claim 5 wherein said diluent is a glycol ether of type (aa).

19. The hydraulic fluid composition of claim 18 wherein said diluent is present in amounts of from about 2 to about 70 percent by weight, based on the total weight of the hydraulic fluid composition.

20. The hydraulic fluid composition of claim 19 wherein said diluent is selected from the group consisting of: diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and tetraethylene glycol monobutyl ether.

21. The hydraulic fluid composition of claim 20 wherein said formal is selected from the group consisting of: [CH O(C H O)] CH [CH O(C l-l.,O) CH 3 z 4 )a]= z, 1 z s z 4 )2]2 2 4 9 2 4 )]2 2, and 4 9 2 4 )a]2 2- 22. The hydraulic fluid composition of claim 18 having incorporated therein from to about 8.0 percent by weight, based on the total weight of the hydraulic fluid composition, of an inhibitor additive for pH and corrosion control.

23. The hydraulic fluid composition of claim 22 wherein from about 0.2 to 6.0 percent by weight of said inhibitor is used.

24. The hydraulic fluid composition of claim 23, wherein said inhibitor is selected from the group consisting of: glycerin, butynediol, diethanolamine, methyl diethanolamine, mixed isopropanolamines, diisopropanolamine and triisopropanolamine.

25. The hydraulic fluid composition of claim 22 wherein from O to about 2 percent by weight, based on the total weight of the hydraulic fluid composition, of an antioxidant additive is incorporated therein.

26. The hydraulic fluid composition of claim 25 wherein from about 0.001 to about 1.0 percent by weight of said antioxidant is used.

27. The hydraulic fluid composition of claim 26 wherein said antioxidant is selected from the group consisting of sodium nitrite and dioctyl diphenylamine.

28. The hydraulic fluid composition of claim 27 wherein said inhibitor is selected from the group consisting of glycerin, butynediol, diethanolamine, methyl diethanolamine, mixed isopropanolamines, diisopropanolamines and triisopropanolamine.

29. The hydraulic fluid composition of claim 28 wherein said formal is selected from the group consisting of a 2 4 )]2 2 a 2 4 )z]z 2 3 2 4 )alz z 5 2 4 )2]z 2 [C4H9 z 4 )]2 2 and 4 9 2 4 )a]2 2- 30. In the operation of a fluid pressure operating device which uses hydraulic pressure transmission fluid, the improvement comprising using as said hydraulic pressure transmission fluid, a composition consisting essentially of (A) a borate ester base fluid selected from the group consisting of (a) a borate ester of the formula:

. wherein R is alkyl of from one to four carbon atoms,

wherein R is alkyl of from one to four carbon atoms, R and R are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with the proviso that one of R and R is methyl and one of R and R is hydrogen; (c) a borate ester of the formula:

wherein R is alkyl of from one to four carbon atoms, R, is a heteric oxyalkylene chain of the formula:

wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula:

wherein T T and T are each an independently selected alkyl group having from one to four carbon atoms; R.,, R R R R and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same; and (B) from about 2 to about 40 percent by weight, based on the total weight of the hydraulic fluid composition, of at least one bis( glycol ether) formal having the for mula:

about 20 to about 96 percent by weight, based on the total weight of the hydraulic fluid composition, of said base fluid. 

2. The hydraulic fluid composition of claim 1 wherein said formal has an alkyl Rb group of one to four carbon atoms, an alkylene Ra group of two to three carbon atoms and x is 1 to
 3. 3. The hydraulic fluid composition of claim 2 wherein from about 2 to about 15 percent by weight, based on the total weight of the hydraulic fluid, of said formal is present.
 4. The hydraulic fluid composition of claim 3 wherein said formal is selected from the group consisting of: (CH3O(C2H4O))2CH2, (CH3O(C2H4O)3)2CH2, (C2H5O(C2H4O)2)2CH2, (C4H9O(C2H4O))2CH2, and (C4H9O(C2H4O)3)2CH2.
 5. The hydraulic fluid composition of claim 2 wherein said base fluid or lubricant is a borate ester of type (a).
 6. The hydraulic fluid composition of claim 5 wherein said base fluid or lubricant consists essentially of from about 20 to about 54.4 percent by weight, based on the total weight of the hydraulic fluid composition.
 7. The hydraulic fluid composition of claim 5 wherein said base fluid or lubricant consists essentially of from about 54.5 to about 92 percent by weight, based on the total weight of the hydraulic fluid composition.
 8. The hydraulic fluid composition of claim 7 wherein said borate ester of type (a) has an alkyl R1 group of one to two carbon atoms and an Ra alkylene group of two to three cArbon atoms.
 9. The hydraulic fluid composition of claim 7 wherein said base fluid or lubricant is a borate ester selected from the group consisting of: (CH3(OCH2CH2)3O)3-B, (C2H5(OCH2CH2)2O)3-B, (C2H5(OCH2CH2)3O)3-B, (C2H5(OCH2CH2)4O)3-B, (C3H7(OCH2CH2)3O)3-B, (C4H9(OCH2CH2)2O)3-B and (C4H9(OCH2CH2)3O)3-B.
 10. The hydraulic fluid composition of claim 9 wherein from about 2 to about 15 percent by weight, based on the total weight of the hydraulic fluid composition, of said formal is used.
 11. The hydraulic fluid composition of claim 10 wherein said formal is selected from the group consisting of: (CH3O(C2H4O))2CH2, (CH3O(C2H4O)2)2CH2, (CH3O(C2H4O)3)2CH2, (C2H5O(C2H4O)2)2CH2, (C4H9O(C2H4O))2CH2 and (C4H9O(C2H4O)3)2CH2.
 12. The hydraulic fluid composition of claim 11 wherein said diluent is present in amounts of from about 2 to about 70 percent by weight, based on the total weight of the hydraulic fluid composition.
 13. The hydraulic fluid composition of claim 12 wherein said diluent is selected from the group consisting of diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and tetraethylene glycol monobutyl ether.
 14. The hydraulic fluid composition of claim 13 wherein from about 0.2 to about 6.0 percent by weight of an inhibitor for pH and corrosion control is used.
 15. The hydraulic fluid composition of claim 14 wherein said inhibitor is selected from the group consisting of glycerin, butynediol, diethanolamine, methyl diethanolamine, mixed isopropanolamines, diisopropanolamine and triisopropanolamine.
 16. The hydraulic fluid composition of claim 15 wherein from about 0.001 to about 1.0 percent by weight, based on the total weight of the hydraulic fluid composition, of an antioxidant is used.
 17. The hydraulic fluid composition of claim 16 wherein said antioxidant is selected from the group consisting of sodium nitrite and dioctyl diphenylamine.
 18. The hydraulic fluid composition of claim 5 wherein said diluent is a glycol ether of type (aa).
 19. The hydraulic fluid composition of claim 18 wherein said diluent is present in amounts of from about 2 to about 70 percent by weight, based on the total weight of the hydraulic fluid composition.
 20. The hydraulic fluid composition of claim 19 wherein said diluent is selected from the group consisting of: diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and tetraethylene glycol monobutyl ether.
 21. The hydraulic fluid composition of claim 20 wherein said formal is selected from the group consisting of: (CH3O(C2H4O))2CH2. (CH3O(C2H4O)2)2CH2, (CH3O(C2H4O)3)2CH2, (C2H5O(C2H4O)2)2CH2, (C4H9O(C2H4O))2CH2, and (C4H9O(C2H4O)3)2CH2.
 22. The hydraulic fluid composition of claim 18 having incorporated therein from 0 to about 8.0 percent by weight, based on the total weight of the hydraulic fluid composition, of an inhibitor additive for pH and corrosion control.
 23. The hydraulic fluid composition of claim 22 wherein from about 0.2 to 6.0 percent by weight of said inhibitor is used.
 24. The hydraulic fluid composition of claim 23, wherein said inhibitor is selected from the group consisting of: glycerin, butynediol, diethanolamine, methyl diethanolamine, mixed isopropanolamines, diisopropanolamine and triisopropanolamine.
 25. The hydraulic fluid composition of claim 22 wherein from 0 to about 2 percent by weight, based on the total weight of the hydraulic fluid composition, of an antioxidant additive is incorporated therein.
 26. The hydraulic fluid composition of claim 25 wherein from about 0.001 to about 1.0 percent by weight of said antioxidant is used.
 27. The hydraulic fluid composition of claim 26 wherein said antioxidant is selected from the group consisting of sodium nitrite and dioctyl diphenylamine.
 28. The hydraulic fluid composition of claim 27 wherein said inhibitor is selected from the group consisting of glycerin, butynediol, diethanolamine, methyl diethanolamine, mixed isopropanolamines, diisopropanolamines and triisopropanolamine.
 29. The hydraulic fluid composition of claim 28 wherein said formal is selected from the group consisting of (CH3O(C2H4O))2CH2, (CH3O(C2H4O)2)2CH2, (CH3O(C2H4O)3)2CH2, (C2H5O(C2H4O)2)2CH2, (C4H9O(C2H4O))2CH2 and (C4H9O(C2H4O)3)2CH2.
 30. In the operation of a fluid pressure operating device which uses hydraulic pressure transmission fluid, the improvement comprising using as said hydraulic pressure transmission fluid, a composition consisting essentially of (A) a borate ester base fluid selected from the group consisting of (a) a borate ester of the formula: (R1(O-Ra)y-O)3-B , wherein R1 is alkyl of from one to four carbon atoms, Ra is alkylene of from two to four carbon atoms and y is an integer of from 2 to 4; (b) a borate ester of the formula: (R1-(OCH2CHR2)m-(OCH2CHR3)nO)3-B , wherein R1 is alkyl of from one to four carbon atoms, R2 and R3 are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with the proviso that one of R2 and R3 is methyl and one of R2 and R3 is hydrogen; (c) a borate ester of the formula: (R1(Rg)O)3-B , wherein R1 is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formula: (- (OCH2CH2)r , (OCH2CHCH3)s -) , wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula:
 31. The process of claim 30 wherein there is from about 2 to about 15 percent by weight, based on the total weight of the hydraulic fluid composition, of said formal.
 32. The process of claim 31 wherein there is from about 20 to about 96 percent by weight, based on the total weight of the hydraulic fluid composition, of said base fluid. 